Turbine Blade Platform Undercut for Stress Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Turbine blades experience high stresses at the joint between the airfoil and the platform, particularly near the airfoil root trailing edge, leading to mechanical loading and vibratory stresses, which existing designs fail to adequately manage.
Innovation Solution
A compound fillet undercut is introduced in the aft portion of the turbine blade's platform to redirect stress loads away from the airfoil trailing edge, featuring a pair of tangent single fillets with a larger first radius and a smaller second radius, forming a compound fillet radius, which reduces stress concentrations and improves flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a traditional platform design is used, then the structure is simple, but high stress concentrations occur at the airfoil trailing edge joint
Solution Approach 1:
The patent applies curvature by introducing a compound fillet undercut with two tangent circular arcs (radii R1 and R2) at the platform trailing edge. This curved geometry redistributes stress flows away from the high-stress airfoil trailing edge joint, reducing stress concentrations while maintaining structural integrity.
Solution Approach 2:
The invention adds a new geometric dimension by creating an undercut feature that extends into the platform thickness. This three-dimensional modification introduces stress relief pathways in the depth direction, effectively redirecting stresses away from the critical airfoil-platform joint interface.
2Strength
If an undercut is added to redirect stresses, then stress concentrations are reduced, but manufacturing complexity increases
Solution Approach 1:
The compound fillet undercut employs two tangent circular arcs (radii R1 and R2) that can be manufactured using standard CNC machining centers or wire EDM processes. The circular geometry is readily achievable with conventional tooling, making the design practical for production while effectively redistributing stresses.
Solution Approach 2:
The patent specifies parameter ranges (R1/R2 ratio of 2.0-2.5, specific dimensional relationships) that optimize both stress redistribution and manufacturability. These parameter guidelines enable consistent fabrication while achieving the desired stress relief effect.
3Strength
If the first radius is made larger than the second radius, then stress redistribution is optimized, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes a specific parameter relationship (R1/R2 ratio between 2.0-2.5) that optimizes stress redistribution while remaining compatible with standard manufacturing tolerances. This ratio guideline provides a practical design rule that balances performance with manufacturability.
Solution Approach 2:
The use of circular arcs with defined radius ratios creates a geometrically stable feature that is insensitive to small dimensional variations. The tangent connection between the two arcs provides a natural transition that reduces sensitivity to machining tolerances.
Data Source
AI summary
A gas turbine blade having reduced stresses around a regions where the airfoil training edge joins the platform is disclosed. The lower stresses are achieved due to an undercut region proximate the blade trailing edge being placed in the platform. The undercut region has a compound fillet radius formed from two single and tangent radii where the first radius closer to the airfoil is larger than the second radius such that a ratio of R1/R2 is approximately 2.0 to 2.5.